The present invention relates to a resistor device for application to a heating element to reduce galvanic action produced in a container by an electrical heating element in which the heating element is used to heat the contents thereof.
Galvanic current flow normally exists between the sheath of the heating element and the wall of the water tank. Failure to control this current results in undue corrosion of the tank wall or sacrificial anode if present. By controlling this current flow, the tank's life can be extended. The particular embodiment of the present invention has been found to be successful in controlling such galvanic flow.
Resistor type devices are known to reduce this galvanic action. In U.S. Pat. No. 2,810,815 by Dicome, a partially exposed resistor is placed generally transverse to the mounting plate of the electric immersion heater apparatus. This patent discloses the construction of the heater assembly incorporating such resistor device. The resistor is built into a terminal block which is used to connect the heating element to the tank. The process of incorporating the resistor into a terminal block involves a number of steps, for example, a cap is required to be placed over the resistor and the terminals which extend from the sheath of the heating element.
Patents such as U.S. Pat. No. 2,947,846 by J. J. Fox relate to heating elements using resistors incorporated in a mounting block structure by soldering, brazing or the like. The correlation between the components of the structure such as the mounting plate and the clamping plate must be maintained to permit proper installation.
The present invention allows the resistor device to be applied as an individual sub-assembly package. This obviates the need for integration of the resistor into other subcomponents and does not require a costly brazing operation.
The resistor device of the present invention may be used in connection with any standard terminal block. Unlike previous devices, the present invention is able to provide resistor type corrosion protection in applications lacking a terminal block or brazed-type compositions.
Conventional heating apparatus generally consist of a heating element of the hairpin type of U-shaped configuration comprising a metal tubular sheath enclosing a heating resistance coil. The heating element sheath conventionally is composed of copper, Type 300 stainless steel, or the like. The heating element is immersed in the liquid to be heated contained in the tank. The terminal portions of the electrical resistance heater are connected to the tank by a screw plug or like mounting means.